2.1. THE COMPLEMENT SYSTEM
The complement system is a group of proteins that constitute about 10 percent of the globulins in the normal serum of humans (Hood, L. E., et al., 1984, Immunology, 2d Ed., The Benjamin/Cummings Publishing Co., Menlo Park, Calif., p. 339). Complement (C) plays an important role in the mediation of immune and allergic reactions (Rapp, H. J. and Borsos, T, 1970, Molecular Basis of Complement Action, Appleton-Century-Crofts (Meredity), New York). The activation of complement components leads to the generation of a group of factors, including chemotactic peptides that mediate the inflammation associated with complement dependent diseases. The sequential activation of the complement cascade may occur via the classical pathway involving antigen-antibody complexes, or by the alternative pathway which involves the recognition of foreign structures such as, certain cell wall polysaccharides. The activities mediated by activated complement proteins include lysis of target cells, chemotaxis, opsonization, stimulation of vascular and other smooth muscle cells, and functional aberrations such as degranulation of mast cells, increased permeability of small blood vessels, directed migration of leukocytes, and activation of B lymphocytes and macrophages (Eisen, H. N., 1974, Immunology, Harper & Row Publishers, Inc. Hagerstown, Md., p. 512).
During proteolytic cascade steps, biologically active peptide fragments, the anaphylatoxins C3a, C4a, and C5a (See WHO Scientific Group, 1977, WHO Tech Rep. Ser. 606:5 and references cited therein), are released from the third (C3), fourth (C4), and fifth (C5) native complement components (Hugli, T. E., 1981, CRC Crit. Rev. Immunol. 1:321; Bult, H. and Herman, A. G., 1983, Agents Actions 13:405).
2.2. COMPLEMENT RECEPTORS
COMPLEMENT RECEPTOR 1 (CR1). The human C3b/C4b receptor, termed CR1 or CD35, is present on erythrocytes, monocytes/macrophages, granulocytes, B cells, some T cells, splenic follicular dendritic cells, and glomerular podocytes (Fearon D. T., 1980, J. Exp. Med. 152:20, Wilson, J. G., et al., 1983, J. Immunol. 131:684; Reynes, M., et al., 1976 N. Engl. J. Med. 295:10; Kazatchkine, M. D., et al., 1982, Clin. Immunol. Immunopathol. 27:210). CR1 specifically binds C3b, C4b and iC3b.
CR1 can inhibit the classical and alternative pathway C3/C5 convertases and act as a cofactor for the cleavage of C3b and C4b by factor I, indicating that CR1 also has complement regulatory functions in addition to serving as a receptor (Fearon, D. T., 1979, Proc. Natl. Acad. Sci. U.S.A. 76:5867; Iida, K. I. and Nussenzweig, V., 1981, J. Exp. Med. 153:1138). In the alternative pathway of complement activation, the bimolecular complex C3b,Bb is a C3 enzyme (convertase). CR1 (and factor H, at higher concentrations) can bind to C3b and can also promote the dissociation of C3b,Bb. Furthermore, formation of C3b,CR1 (and C3b,H) renders C3b susceptible to irreversible proteolytic inactivation by factor I, resulting in the formation of inactivated C3b (iC3b). In the classical pathway of complement activation, the complex C4b,2a is the C3 convertase.
CR1 (and C4 binding protein, C4bp, at higher concentrations) can bind to C4b, and can also promote the dissociation of C4b,2a. The binding renders C4b susceptible to irreversible proteolytic inactivation by factor I through cleavage to C4c and C4d (inactivated complement proteins).
CR1 has been shown to have homology to complement receptor type 2 (CR2) (Weis, J.J., et al., 1986, Proc. Natl. Acad. Sci. U.S.A. 83:5639-5643). CR1 is a glycoprotein comprising multiple short consensus repeats (SCRs) arranged in 4 long homologous repeats (LHRs). The most C-terminal LHR called LHR-D is followed by 2 additional SCRs, a transmembrane region and a cytoplasmic region (Klickstein, et al., 1987, J. Exp. Med., 165:1095; Klickstein, et al. 1988, J. Exp. Med., 168:1699-1717). Erythrocyte CR1 appears to be involved in the removal of circulating immune complexes in autoimmune patients and its levels may correlate with the development of AIDS (Inada, et al., 1986, AIDS Res. 2:235; Inada, et al., 1989, Ann. Rheu. Dis. 4:287).
Four allotypic forms of CR1 have been found, differing by increments of 40,000-50,000 daltons molecular weight. The two most common forms, the F and S allotypes, also termed the A and B allotypes, have molecular weights of 250,000 and 290,000 daltons respectively, (Dykman, T. R., et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80:1698; Wong, W. W., et al., 1983, J. Clin. Invest. 72:685), and two rarer forms have molecular weights of 210,000 and 290,000 daltons (Dykman, T. R., et al., 1984, J. Exp. Med. 159:691; Dykman, T. R., et al., 1985, J. Immunol. 134:1787). These differences apparently represent variations in the polypeptide chain of CR1, rather than glycosylation state, because they were not abolished by treatment of purified receptor protein with endoglycosidase F (Wong, W. W., et al., 1983, J. Clin. Invest. 72:685), and they were observed when receptor allotypes were biosynthesized in the presence of the glycosylation inhibitor tunicamycin (Lublin, D. M., et al., 1986, J. Biol. Chem. 261:5736). All four CR1 allotypes have C3b-binding activity (Dykman, T. R., et al., 1983, Proc. Natl. Acad. Sci. U.S.A. 80:1698; Wong, W. W., et al., 1983, J. Clin. Invest. 72:685; Dykman, T. R., et al., 1984, J. Exp. Ned., 159:691; Dykman, T. R., et al., 1985, J. Immunol. 134:1787). There are four LHRs in the F (or A) allotype of .about.250 kD, termed LHR-A, -B, -C, and -D, respectively, 5' to 3' (Wong, et al., 1989, J. Exp. Med. 169:847). While the first two SCRs in LHR-A determine its ability to bind C4b, the corresponding units in LHR-B and -C determine their higher affinities for C3b. The larger S (or B) allotype of .about.290 kd has a fifth LHR that is a chimera of the 5' half of LHR-B and the 3' half of LHR-A and is predicted to contain a third C3b binding site (Wong, et al., 1989, J. Exp. Med. 169:847). The smallest F' (or C) allotype of CR1 of .about.210 kD, found in increased incidence in patients with systemic lupus erthematosis (SLE) and associated with patients in multiple lupus families (Dykman, et al., 1984, J. Exp. Med. 159:691; Van Dyne, et al., 1987, Clin. Exp. Immunol. 68:570), may have resulted from the deletion of one LHR and may be impaired in its capacity to bind efficiently to immune complexes coated with complement fragments.
A naturally occurring soluble form of CR1 has been identified in the plasma of normal individuals and certain individuals with SLE (Yoon, et al., 1985 J. Immunol. 134:3332-3338). Its structural and functional characteristics are similar to those of erythrocyte (cell surface) CR1, both structurally and functionally. Hourcade, et al. (1988, J. Exp. Med. 168:1255-1270) also observed an alternative polyadenylation site in the human CR1 transcriptional unit that was predicted to produce a secreted form of CR1 containing the C4b binding domain.
Several soluble fragments of CR1 have also been generated via recombinant DNA procedures by eliminating the transmembrane region from the DNAs being expressed (Fearon, et al., International Patent Publication No. WO89/09220, Oct. 5, 1989; Fearon, et al., International Patent Publication No. WO91/05047, Apr. 18, 1991). The soluble CR1 fragments were functionally active, bound C3b and/or C4b and demonstrated factor I cofactor activity, depending upon the regions they contained. Such constructs inhibited in vitro the consequences of complement activation such as neutrophil oxidative burst, complement mediated hemolysis, and C3a and C5a production. A soluble construct sCR1/pBSCR1c, also demonstrated in vivo activity in a reversed passive Arthus reaction (Fearon, et al., 1989, supra; Fearon, et al., 1991, supra; Yeh, et al., 1991 supra), suppressed post ischemic myocardial inflammation and necrosis (Fearon, et al., .sup.1989, supra; Fearon, et al., 1991, supra; Weismann, et al., 1990, Science, 249:146-151) and extended survival rates following transplantation (Pruitt and Bollinger, 1991, J. Surg. Res. 50:350; Pruitt, et al., 1991, Transplantation 52:868). [Mulligan et al, 1992, J. Immunol. 148:3086-3092 (injury following immune complex deposition). Mulligan, et al., 1992, J. Immunol. 148:1479-1485 (protection from neutrophil mediated tissue injury). Lindsay, et al., 1992, Annals of Surg. 216:677. , Hill, et al., 1992, J. Immunol. 149:1722-1728 (tissue ischemia reperfusion injuries)].
CR2. Complement receptor type 2 (CR2, CD21) is a transmembrane phosphoprotein consisting of an extracellular domain which is comprised of 15 or 16 SCRs, a 24 amino acid transmembrane region, and a 34 amino acid cytoplasmic domain (Moore, et al., 1987, Proc. Natl. Acad. Sci. U.S.A. 84:9194-9198; Weis, et al., 1988, J. Exp. Med. 167:1047-1066). Electron microscopic studies of soluble recombinant CR2 have shown that, like CR1, it is an extended, highly flexible molecule with an estimated contour length of 39.6 nanometers by 3.2 nanometers, in which each SCR appears as a ringlet 2.4 nanometers in length (Moore, et al., 1989, J. Biol. Chem. 34:20576-20582).
By means of recombinant DNA experiments with eukaryotic expression vectors expressing deletion or substitution mutants of CR2 in COS cells, the ligand 30 binding sites of CR2 have been localized to the two N-terminal SCR's of the molecule (Lowell, et al., 1989, J. Exp. Med. 170:1931-1946). Binding by cell surface CR2 of the multivalent forms of C3 ligands such as iC3b and C3dg causes activation of B-cells (Melchers, et al., 1985, Nature, 317:264-267; Bohnsack, et al., 1988, J. Immunol. 141:457-463; Carter, et al., 1988, J. Immunol. 143:1755-1760).
A form of recombinant soluble CR2 has been produced (Moore, et al., 1989, J. Biol. Chem. 264:20576-20582). In analogy to the soluble CR1 system, soluble CR2 was produced in a recombinant system from an expression vector containing the entire extracellular domain of the receptor, but without the transmembrane and cytoplasmic domains. This recombinant CR2 is reported to bind to C3dg in a 1:1 complex with Kd equal to 27.5 mM and to bind to the Epstein-Barr proteins gp350/220 in a 1:1 complex with a Kd of 3.2 nM (Moore, et al., 1989, J. Biol. Chem. 264:20576-20582).
CR3. A third complement receptor, CR3, also binds iC3b. Binding of iC3b to CR3 promotes the adherence of neutrophils to complement-activating endothelial cells during inflammation (Marks, et al., 1989, Nature 339:314). CR3 is also involved in phagocytosis, where particles coated with iC3b are engulfed by neutrophils or by macrophages (Wright, et al., 1982, J. Exp. Med. 156:1149; Wright, et al., 1983, J. Exp. Med. 158:1338).
CR4. CR4(CD11) also appears to be involved in leukocyte adhesion (Kishimoto, et al., 1989, Adv. Immunol. 46:149-82).
DAF. DAF, or decay-accelerating factor, is a membrane protein that appears to have similar action to C4Bp in bringing about a functional-dissociation of C2b from C4b. DAF is linked to membranes via a phosphatidyl inositol glycolipid, and its absence from red blood cells has been shown to be a major causative factor in paroxysmal nocturnal hemoglobinuria. (Encyclopedia of Human Biology, Academic Press, Inc. 1991). DAF binds to C3b/C4b as well as C3 convertases (EP 0512 733 A2).
DAF contains 4 SCRs followed by an O-linked glycosylation region, and is terminated with a glycolipid anchor (EP 0512 733 A2). Cells that express DAF show substantial increases in resistance to complement-mediated cell lysis (Lublin, D. M. et al., 1991, J. Exp. Med. 174:35; Oglesby, T. J., et al., 1991; Trans. Assoc. Am. Phys. CIV:164-172; White, D. J. G., et al., 1992; Transplant Proc. 24:474-476).
MCP. MCP or membrane cofactor protein, like DAF, contains 4 SCRs followed by an O-linked glycosylation region. MCP is terminated witn an extra cytoplasmic segment (whose importance is unknown) a transmembrane region and an intracellular domain (EP 0512 733 A2). Also, like DAF, cells expressing NCP confer substantial increases in resistance to complement-mediated cell lysis. (EP 0512 733 A2 and Lublin, D. M., et al., J. Exp Med (19) 174:35; Oglesby, T. J. et al., Trans Assoc Am Phys (1991) CIV:164-172; White, D. J. G., et al., Transplant Proc (1992) 24:474-476).
FACTOR H. Factor H is a plasma protein that is exclusively or predominantly composed of SCRs (Chung, L. P., et al., 1985, Biochem. J. 230:133; Kristensen, T., et al., 1986, J. Immunol. 136:3407). Factor H is a regulator of the alternative pathway. Factor H binds to C3b and to the C3b portion of C3 convertases (C3b, Bb) (Encyclopedia of Human Biology, supra) accelerating dissociation of Bb from these complexes thereby inactivating them. Factor H also regulates the use of C5 in the classical pathway by competing with C5 for binding to C3b, thus inactivating the activity of the C3/C5 convertase (Encyclopedia of Human Biology, supra).
2.3. SELECTINS AND SELECTIN LIGANDS
Selectins are a group of cell surface glycoproteins which characteristically display a NH.sub.2 terminal lectin domain related to the carbohydrate recognition structure described for animal lectins, an epidermal growth factor domain, and a domain consisting of short repeating sequences analogous to those found in the complement regulatory proteins which map to a region of chromosome 1 called the regulators of complement activity (RCA) (Harlan & Liu, Adhesion: Its Role in Inflammatory Disease, W. H. Freeman & Co., 1992). Three independently studied selecting have been characterized and are named according to the cell type upon which each was originally identified. Under the current nomenclature there are the E-selectins, originally identified on cytokine-activated endothelial cells (Bevilacque, M. P. et al., (1985) J. Clin. Invest. 76:2003-2011); P-selectins, discovered on activated platelets (Hsu-Lin, P. E., et al. (1984) J. Biol. Chem. 259:9121-9126); and finally, L-selectins recognized as a cell surface marker on most leukocytes including lymphocytes, neutrophils, and monocytes (Kansas, G. S. et al., (1985) J. Immunol. 134:2995-3002). Each selectin has been implicated as a key factor in important events in cellular adhesion and recognition. As such, their carbohydrate recognition structures at the NH.sub.2 -terminal portion of the molecule as well as their carbohydrate ligands have been extensively studied.
Selectins, then, are cell adhesion molecules that in inflammatory situations are responsible for the attachment of platelets and leukocytes to vascular surfaces and their subsequent infiltration into the tissue. During a normal inflammatory response the leukocytes, in responding to various signals, enter the tissue and phagocytize invading organisms. In various pathologic inflammatory diseases, such as psoriasis and rheumatoid arthritis, this response may lead to serious organ tissue damage. Similarly, in reperfusion injury, invading leukocytes are responsible for tissue damage. And, aside from their involvement in inflammation, cell adhesion molecules on selecting play a central role in other diseases such as tumor metastasis.
In inflammatory situations, all three selecting are implicated in the recruitment of leukocytes to the site of inflammation. Early events in the inflammatory response include the recruitment of neutrophils to the site of tissue damage. In normal situations, circulating lymphocytes bind to the vascular endothelium with low avidity. Under situations of distress however, as when the body has been invaded by a bacterial pathogen or when tissue damage has occurred, leukocytes interact with the activated endothelium in another manner. First, up regulation of selecting on endothelial cells and platelets occurs to control the localization of leukocytes to the inflamed endothelium. The initial step of attachment of neutrophils to the endothelial cells lining the venules is controlled by selecting and is known as neutrophil "rolling" (von Andrian, U. H. et al., (1991) Proc. Natl. Acad. Sci., U.S.A. 88:7538-7542; Smith, C. W., et al., (1991) J. Clin. Invest., 87:609-618). This "rolling" precedes the firm adhesion of leukocytes, especially neutrophils to the endothelium which is controlled by a different class of receptors known as the integrins. (Lawrence, M. B. and Springer, T. S. (1991) Cell 65: 859-873; von Andrain, U. H. et al., (1991) Proc. Natl. Sci. U.S.A. 88:7538-7542; Larson R. S. and Springer, T. A. (1990) Immunol. Rev. 114:181-217). Extravasation of the cells into the surrounding tissue proceeds after the aforementioned attachment processes have each been accomplished.
One of the selecting, E-selectin (ELAM-1, endothelial cell adhesion molecule, LECCAM-2) is expressed on endothelial cells following induction by cytokines such as interleukin-1.beta., tumor necrosis factor-.alpha., lymphotoxin, bacterial endotoxins, interferon-.gamma. and the neuropeptide substance-p (Harlan & Liu, supra). The expression of E-selectin on activated endothelium requires de novo synthesis, peaks at 4-6 hours, and persists from 2-48 hours after initial stimulus. Activated endothelia expressing the ELAM-1 receptor have been shown to bind neutrophils (Bevilacque M. P., et al. (1987) Proc. Natl. Acad. Sci. U.S.A. 84:9238-9242); monocytes (Walz, G. et al., (1990) Science 250: 1132-1135): eosinophil (Kyan-Aung (1991) J. Immunol. 146:521-528): and NK cells (Goelz, S. E. (1990) Cell 63:1149-1356). Additionally, activated endothelium binds some carcinoma cells (Rice, G. E. and Bevilacqua M. P. (1989) Science 246:1303-1306; Walz, G. et al., (1990) 250 1132-1135) implicating a role for E-selectins in attachment of tumor cells to blood vessel walls.
P-selectin (CD62, granule membrane protein-140, GMP-140, platelet activation dependent granule external membrane, Padgem, LECCAM-3) is expressed on activated platelets as well as endothelial cells. The P-selectin expression can be mobilized from intracellular stores in minutes after activation. P-selectins bind neutrophils and monocytes, as well as carcinoma cells (Walz, G., et al., (1990) 250:1132-1135).
P-selectin, or CD62 expression does not require de novo synthesis because this selectin is stored in secretory granules, also called Weibel-Palade bodies, in both platelets and endothelial cells. Thus, within minutes of activation of either cell type, for example by thrombin, histamine, or phorbol esters, CD62 is rapidly transported to the surface of the cell where it can bind the ligand found on neutrophils, monocytes, and other cells, These ligand-bearing cells then adhere to the platelet or endothelial cells expressing the CD62 receptor.
Patel et al. have found that endothelial cells also express CD62 in response to low levels of hydrogen peroxide or other oxidizing agents through the production of free radicals (Patel et al., 1991, J. Cell Biol. 112:749-759). While endothelial cells normally reinternalize CD62 within minutes of activation, induction by free radicals produces prolonged expression of the selectin. Because neutrophils release oxidizing agents and free radicals following activation, initial recruitment of neutrophils by transiently expressed CD62 could effectively prolong the expression of CD62 through free radical generation by neutrophils (Harlan & Liu, Adhesion, supra).
L-selectin, (lymphocyte homing receptor, LECCAM-1, Mel-14, Leu-8, TQ-1, Ly-22, LAM-1) is constitute expressed on the cell surface and is shed after activation (Jung. T. M. et al., (1988) J. Immunol., 141:4110-4117).
Recent advancements in the field of adhesion molecules have led to the understanding of the role of protein-carbohydrate interactions. In particular, the ligands for selectins have been recently studied (Bevilaque, M. P. and Nelson, R. M. (1993) J. Clin. Invest. 91: 379-387). Among the ligands identified are the Lewis X blood antigen (Le.sup.x) and sialylated Lewis X antigen. The Lewis X antigens have been known for some time, and had been identified as the terminal structures on cell surface glycoproteins and glycolipids or neutrophils and promyelocytic cell lines (Harlan & Liu, Adhesion, supra).
Lowe et al. demonstrated that transfection of a cDNA for the Lewis blood group fucosyl transferase (Gal.beta.1,3/4GlcNAca1,3 fucosyltransferase) into Chinese hamster ovary (CHO) cells resulted in the expression of the Le.sup.x and SLe.sup.x antigens and the simultaneous ability of the transfected cells to adhere to E-selectins on TNF-.alpha.-activated human umbilical vein endothelial cells (HUVECs) (Lowe et al., 1990, Cell 63:475-484). Sialidase treatment of the cells abolished their ability to adhere to activated HUVECs, indicating that a sialylated structure was required for adhesion. Additionally, it was observed that a pre-myelocytic leukemia-60 (HL-60) cell clone which expressed SLe.sup.x bound to HUVECS while another clone that did not express SLe.sup.x did not bind to HUVECS.
Phillips et al. produced CHO glycosylation mutants, which, unlike the wild-type cells, expressed fucosyltransferase activities that synthesized both Le.sup.x and SLe.sup.x (LEC11) or Le.sup.x only (LEC12) as terminal sugar structures on cell surface glycoproteins (Phillips et al., 1990 Science 250:1130-1132). Only LEC11 cells bound to E-selectin on activated HUVECs, and the adhesion was abolished by pretreatment of the LEC11 cells with sialidase, implicating SLe.sup.x as the ligand.
The nucleic acid sequence of an .alpha.1,3-fucosyl transferase responsible for adding a fucosyl residue to an appropriate carbohydrate such as ELAM, through an .alpha.1,3 glycosidic linkage has been reported (International Patent Publication No. WO91/16900). This report also describes recombinant COS and CHO cells transformed with the transferase.
Other ligands that bind to selectins have also been disclosed. These ligands structurally resemble the Lewis X antigens (International Patent Publication No. WO92/02527 and International Patent Publication No. WO91/19502).
2.4. DISEASES INVOLVING INAPPROPRIATE COMPLEMENT ACTIVITY
Diminished expression of CR1 on erythrocytes of patients with systemic lupus erythematosus (SLE) has been reported by investigators from several geographic regions, including Japan (Miyakawa, et al., 1981, Lancet 2:493-497; Minota, et al., 1984, Arthr. Rheum. 27:1329-1335), the United States (Iida, et al., 1982, J. Exp. Med. 155:1427-1438; Wilson, et al., 1982, N. Engl. J. Med. 307:981-986) and Europe (Walport, et al., 1985, Clin. Exp. Immunol. 59:547; Jouvin, et al., 1986, Complement 3:88-96; Holme, et al., 1986, Clin. Exp. Immunol. 63:41-48). CR1 number has also been found to correlate inversely with serum levels of immune complexes, with serum levels of C3d, and with the amounts of erythrocyte-bound C3dg, perhaps reflecting uptake of complement-activating immune complexes and deposition on the erythrocyte as an "innocent bystander" (Ross, et al., 1985, J. Immunol. 135:2005-2014; Holme, et al., 1986, Clin. Exp. Immunol. 63:41-48; Walport, et al., 1985, Clin. Exp. Immunol. 59:547).
Abnormalities of complement receptor expression in SLE are not limited to erythrocyte CR1. Relative deficiencies of total cellular CR1 of neutrophils and plasma membrane CR1 of B lymphocytes of the SLE patients have been shown to occur (Wilson, et al., 1986, Arthr. Rheum. 29:739747).
The relative loss of CR1 from erythrocytes has also been observed in patients with Human Immunodeficiency Virus (HIV) infections (Tausk, F. A., et al., 1986, J. Clin. Invest. 78:977-982) and with lepromatous leprosy (Tausk, F. A., et al., 1985, J. Invest. Dermat. 85:58s-61s).
Complement activation has also been associated with disease states involving inflammation. The intestinal inflammation of Crohn's disease is characterized by the lymphoid infiltration of mononuclear and polymorphonuclear leukocytes. It was found recently (Ahrenstedt, et al., 1990, New Engl. J. Med. 322:1345-9) that the complement C4 concentration in the jejunal fluid of Crohn's disease patients increased compared to normal controls. Other disease states implicating the complement system in inflammation include thermal injury (burns, frostbite) (Gelfand, et al., 1982, J. Clin. Invest. 70:1170; Demling, et al., 1989, Surgery 106:52-9), hemodialysis (Deppisch, et al., 1990, Kidney Inst. 37:696-706; Kojima, et al., 1989, Nippon Jenzo Gakkai Shi 31:91-7), and post pump syndrome in cardiopulmonary bypass (Chenoweth, et al., 1981, Complement Inflamm. 3:152-165; Chenoweth, et al., 1986, Complement 3:152-165; Salama, et al., 1988, N. Engl. J. Med. 318:408-14). Both complement and leukocytes are reported to be implicated in the pathogenesis of adult respiratory distress syndrome (Zilow, et al., 1990, clin Exp. Immunol. 79:151-57; Langlois, et al., 1989, Heart Lung 18:71-84). Activation of the complement system is suggested to be involved in the development of fatal complication in sepsis (Hack, et al., 1989, Am. J. Med. 86:20-26) and causes tissue injury in animal models of autoimmune diseases such as immune complex-induced vasculitis (Cochrane, 1984, Springer Seminar Immunopathol. 7:263), glomerulonephritis (Couser et al, 1985, Kidney Inst. 29:879), hemolytic anemia (Schreiber and Frank, 1972, J. Clin. Invest. 51:575), myasthenia gravis (Lennon, et al., 1978, J. Exp. Med. 147:973; Biesecker and Gomez, 1989, J. Immunol. 142:2654), type II collagen-induced arthritis (Watson and Townes, 1985, J. Exp. Med. 162:1878), and experimental allergic and hyperacute xenograft rejection (Knechtle, et al., 1985, Heart Transplant 4(5):541; Guttman, 1974, Transplantation 17:383; Adachi, et al., 1987, Trans. Proc. 19(1):1145). Complement activation during immunotherapy with recombinant IL-2 appears to cause the severe toxicity and side effects observed from IL-2 treatment (This, et al., 1990, J. Immunol. 144:2419).
Complement may also play a role in diseases involving immune complexes. Immune complexes are found in many pathological states including but not limited to autoimmune diseases such as rheumatoid arthritis or SLE, hematologic malignancies such as AIDS (Taylor, et al., 1983, Arthritis Rheum. 26:736-44; Inada, et al., 1986, AIDS Research 2:235-247) and disorders involving autoantibodies and/or complement activation (Ross, et al., 1985, J. Immunol. 135:2005-14).
Soluble CR1 has been successfully used to inhibit complement activation In a number of animal models: Moat, B. P., et al., 1992, Amer. Review of Respiratory disease 145:A845; Mulligan, M. S., et al., 1992, J. Immunol. 148:1479-1485; Yeh, C. G. et. al., 1991, J. Immunol. 146 250-256; Weisman, et al., 1990, Science 249:146-51; Pruitt, et al., 1991, Transplantation 52(5):868-73; Pruitt and Bollinger, 1991, J. Surg. Res. 50:350-55; Rabinovici, et al., 1992, J. Immunol. 149:1744-50; Mulligan, et al., 1992, J. Immunol. 148:1479-1485; Lindsay, et al., 1992, Annals of Surg. 216:677.
Studies of Weisman et al (1990, Science 249:146-151) have demonstrated that sCR1 can prevent 90% of the generation of C3a and C5a in human serum activated by the yeast cell wall component zymosan. Weisman, et al. (1990, supra) also utilized sCRI in the rat to inhibit complement activation and reduce the damage due to myocardial infarction. Soluble CR1 also appears to inhibit the complement dependent process of the reverse Arthus reaction (Yeh, et al., 1991, J. Immuno. 146:250-256), and hyperacute xenograft rejection (Pruitt, et al., 1991, Transplantation 52:868-873). Recent data (Moat, et al., 1992, Amer. Rev. Respiratory Disease 145:A845) indicate that sCR1 is of value in preventing complement activation in an experimental model of cardiopulmonary bypass in the pig, a situation where complement activation has been demonstrated.
Citation or identification of any reference of Section 2 of this application shall not be constructed as an admission that such reference is available as prior art to the present invention.